Speaking of TrueCrypt, is it possible to have encrypted volumes / directories on a system that can not be detected? That is, if I breeze through TSA, and Customs decides they want to make an "image" of my drive...

I'm really not interested in being detained for refusing to give up the access codes.

I'd rather they didn't know there was an encrypted dir or partition or volume at all.

Is TrueCrypt Windows only? It would have to be, wouldn't it? Is there a similar app for Linux?